PostgreSQL 返回多个结果集

MySQL的存储过程 可以很方便的一次性的返回多个结果集， 但是POSTGRESQL目前不提供这样的功能。
一个直译的方法就是用游标来做，不过也可以把结果集放到数组里面或者一个大的临时表或者是XML等的格式来输出。


比如在MySQL里面可以这样简单的写一个存储过程。

delimiter ||
create procedure sp_get_multiple_set1()
begin


  select * from j1 limit 20;
  select * from tmp_2 limit 20;
end;
||
delimiter ;


执行下会得到两个结果集。
t_girl--call sp_get_multiple_set1();
+------+------+
| id   | str1 |
+------+------+
|    1 | love |
|    2 | hate |
+------+------+
2 rows in set (0.00 sec)


+------+---------------+
| id   | register_date |
+------+---------------+
|    1 | 2014-01-18    |
|    2 | 2014-01-03    |
|    3 | 2014-01-16    |
+------+---------------+
3 rows in set (0.00 sec)


Query OK, 0 rows affected (0.00 sec)


t_girl--

在PostgreSQL环境下，来看下下面的函数代码，只能用游标来实现，而且还不能在函数里面返回。

create or replace function sp_get_multiple_set1(
IN f_id int,
refcursor,
refcursor
) returns setof refcursor
as
$ytt$
declare r1 alias for $2;
               r2 alias for $3;
begin
   open  r1 for select * from j1 where id =f_id;
   return next r1;
   open r2 for select * from tmp_2 where id = f_id;
   return next r2;


end;
$ytt$ language plpgsql;

接下来，在一个事务里面来获取对应的游标结果集。

t_girl=# begin;
BEGIN
t_girl=# select * from sp_get_multiple_set1(1,"a"::refcursor,"b"::refcursor);
 sp_get_multiple_set1 
----------------------
 a
 b
(2 rows)


t_girl=# fetch all from a;
 id | str1 
----+------
  1 | love
(1 row)


t_girl=# fetch all from b;
 id | register_date 
----+---------------
  1 | 2013-01-20
(1 row)


t_girl=# close a;
CLOSE CURSOR
t_girl=# close b;
CLOSE CURSOR
t_girl=# commit;
COMMIT
t_girl=#

如果是是多个结果集，但是每个结果集里面只有一行数据的话，也可以用OUT参数来实现。

create or replace function sp_get_single_set2(
f_id int,
IN refcursor,
IN refcursor,
OUT r3 ytt_j1,
OUT r4 ytt_tmp_2
) returns  record
as
$ytt$
declare r1 alias for $2;
              r2 alias for $3;
begin
   open  r1 for select * from j1 where id =f_id;
   open r2 for select * from tmp_2 where id = f_id;
   
   loop
      fetch r1 into r3;
      fetch r2 into r4;
      exit when not found;
      return;
   end loop;
   close r1;
   close r2;
end;
$ytt$ language plpgsql;

t_girl=# select * from sp_get_multiple_set2(1,"a"::refcursor,"b"::refcursor);
    r3    |       r4       
----------+----------------
 (1,love) | (1,2013-01-20)
(1 row)


t_girl=# 

如果返回的多个结果集的字段和类型都一致的话，那就跟单个结果集一样了。